Building Seawall- Wet Footers?

[Grandmotherbear]

We got a permit to build a seawalll at the lake to hold in the sand I am ordering to replace the 5 feet or so that the hurricanes chewed out. As I explained to the the nice government official, we aren't burdened with any preconceived notions of how to accomplish this goal. He thought it would be best to have the sand delivered and bulldozed and dig the footrs, then use cb and rebar with bracing to the landward side. I got home and realized- the footers will probably have to be poured into water. The lake level is not dropping as fast as it has in past years. (builds to a high water mark during the rainy season and then drops during the dry season) This means that I will probably be digging a trench into water ( or the guy with a cat, if I can find one). Not being burdened much with building knowledge, my question to the board buddies is

1. If I pour concrete into a space where there is water in the bottom of the form, will it set up?
2. Should the footer be cb and concrete, or just concrete with the cb, rebar and concrete filling on top?

My plan was to slope the sand and build a wall down into the sand, with sodding and wild lake grasses laid on the new sand. I figured the lake would eventually erode the sand on the lake side of the wall , hopefully the seawall would keep it from eating any more of our lot.

We also have the dock sitting about 4 feet out into the water and I thought I would just build a cb/rebar /concrete structure from a little before the planned seawall to the dock- it's in water about 3 feet deep at the shallowest. Must I wait for the feet of the dock to be dry and exposed, or can I work in standing water?

I can't contract this out- the permit is only good for 6 months and the waiting list for seawall construction in this srea is 6-9 months due to all the hurricane damage. Any comments, thoughts, etc, are much appreciated.

[SteveD(TX)]

The concrete will generally harden, but the strength will be compromised if you just use regular concrete. The best technique would be to wait until the area is dry, or build a coffer dam to keep out the water, then pump the water out of the enclosure before you pour. Water will generally seep in, but if the area is continuously pumped the mix should set up adequately. This method is time-consuming and expensive to do correctly though.

There are specialty concrete mixtures on the market that are designed to be poured into wet areas, but I have not tried them. I believe that they are referred to as plastic concrete or plasticrete(?). You might have to go to a co. that specializes on concrete to get it because I couldn't find it in the regular home improvement stores. Perhaps there is a similar additive for regular concrete or cement; I don't know. Good luck and let us know how the project comes out.

[greg273]

there is a method called 'seacrete' which involves running electric current thru a steel mesh, the dissolved minerals in the sea water form basically concrete! I've never actually seen it, only heard of it being used. Also, wont the salts in seawater mess up regular concrete? Being a landlubber i wouldnt know too much about that... but the seacrete thing is legit, as far as i know

[Ed in S. AL]

Why do you need to use concrete? Have you looked at the new heavy duty plastic sea wall material? We put it in at my father-in-laws, and it is great. Light weight, and easy to install.

[Grandmotherbear]

Greg- Lake Placid is freshwater, not salt. About the only minerals are iron, calcium, and whatever is in agricultural chemicals.
Ed - WHAT is the seawall material called, where did you get it and will it stand up to hurricane force winds and waves? We had 6 foot waves on the lake during the Great March Storm that became The Perfect Storm when it hit New England. Do you have a site link? I'm all ears!!!

[Ed in S. AL]

It's called vinyl seawall. We have actually did two seawalls with it.This stuff is about a half inch thick gray plastic. It was really great to use. Kind of slipped together like mobile home skirting. It has taken a beating from 3 hurricanes now, and hasn't moved a hair. During Hurricane Ivan, it was under 8 feet of water, and stayed in place. You can form up and pour concrete on the top of it. We sank treated post behind it, and layed a wood top over it. Comes in sheets up to 40 feet long.

Seawall

[Grandmotherbear]

Thanks! I read the link, Grandfatherbear read the link, and we have emailed the manufacturer to find out if there are any providers/contractors in the Lake Placid area!